Maynilad has the responsibility to operate, maintain and invest in the water and sewerage system of the 17 cities and municipalities that comprise the West Zone. These areas include: Caloocan, Las Piñas, Malabon, Manila, Muntinlupa, Navotas, Pasay, Parañaque, Valenzuela, parts of Quezon City, a part of Makati, Cavite City, and the municipalities of Rosario, Imus, Noveleta, Bacoor, and Kawit in Cavite.

The West Zone covers a total of 540.43 square kilometers. To manage the delivery of water and wastewater services in its coverage area, Maynilad divided the West Zone into 16 Business Areas (BA) that are further broken down into zones, sub-zones and District Metering Areas (DMAs).